Photovoltaic cells can be made using p-type chalcogenide based materials as absorber layers which convert incident light or radiation to electrical energy. These p-type chalcogenides are typically selenides, sulfides or sulfide selenides of at least one, and more typically at least two or three of the following metals: Cu, In, Ga, Al (referred to herein as CIS, CISS, CIAS, CIASS, CIGS, CIGSS, or CIAGSS depending upon the combination of elements used). Using a CdS based buffer layer near or adjacent to the p-type chalcogenide is also known.
It is known that CdS layers can be formed on various substrates by chemical bath deposition, physical vapor deposition or sputtering. See e.g. Abou-Ras et al (Thin Solid Films 480-481 (2005) 118-123) and U.S. Pat. No. 5,500,055. Abou-Ras specifically looked at the effect of deposition method comparing CBD deposition to PVD deposition and observed that CBD deposition of the CdS created more efficient cells compared with cells made with PVD. Abou-Ras proposes that the lack or decrease of interdiffusion at the CIGS-CdS interface in the case of PVD deposited cells is a reason for their decreased efficiencies.